Product Name: Famciclovir
Common Brand Names: Famvir
Pharmaceutical Category: Antivirals
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There is an additional general information about this medication active ingredient famciclovir:
Famciclovir is an antiviral drug. After oral administration, famciclovir is rapidly converted in vivo to penciclovir, which has in vivo and in vitro activity against human herpes viruses, including virus Varicella zoster and Herpes simplex types 1 and 2, and Epstein-Barr virus and cytomegalovirus.
Penciclovir enters the virus-infected cells, where under the influence of viral thymidine kinase is rapidly converted to the monophosphate, which, in turn, with the participation of cellular enzymes becomes triphosphate. Penciclovir triphosphate in virus-infected cells more than 12 hours, suppressing their viral DNA synthesis and replication of viruses. The half-life of penciclovir triphosphate in cells infected with Varicella zoster, Herpes simplex, is 9, 10 and 20 hours respectively. The concentration of penciclovir triphosphate in uninfected cells is less than the minimum defined, so that therapeutic concentrations of penciclovir has no effect on uninfected cells.
Penciclovir is active against newly discovered strains resistant to acyclovir Herpes simplex virus with altered DNA polymerase.
Famciclovir significantly reduces the intensity and duration of postherpetic neuralgia in patients with herpes zoster.
After oral administration Famciclovir is rapidly and almost completely absorbed and rapidly converted to the active penciclovir. The bioavailability of penciclovir after oral administration of famciclovir is 77%. At famciclovir doses 125 mg, 250 mg or 500 mg penciclovir Cmax is reached after an average of 45 minutes. With repeated administration of the drug an accumulation were not observed. The plasma protein binding of penciclovir and its 6-deoxy precursor is less than 20%.
T1/2 of penciclovir in the final phase of the plasma after a single and repeated doses of about 2 hours.
Famciclovir appears mostly in the form of penciclovir and its 6-deoxy precursor, which are excreted in the urine in unchanged form, famciclovir in the urine is not detected.
Why is Famciclovir prescribed?
Infections caused by the virus Varicella zoster (shingles, including herpes zoster with ophthalmic complications); infection caused by the virus Herpes simplex (primary infection, exacerbation of chronic infection, suppression of recurrent infection).
Dosage and administration
The treatment by Famciclovir should begin immediately after diagnosis.
For oral administration the single dose is 250-500 mg. The frequency and duration of use depends on the evidence, the state of immunity, kidney function, the effectiveness of treatment.
Famciclovir side effects, adverse reactions
Possible: weak and moderate headaches, nausea.
Rarely: vomiting, dizziness, skin rash; mostly in elderly patients - confusion, hallucinations.
In patients with lowered immunity: possible abdominal pain, fever, rarely - granulocytopenia and thrombocytopenia.
Hypersensitivity to famciclovir and penciclovir.
Using during pregnancy and breastfeeding
Because a safety of famciclovir in pregnancy and lactation has not been studied, the usage of this drug is not recommended, except in cases where the expected benefits of therapy to the mother outweighs the potential risk to the fetus or infant.
It is not known whether penciclovir is excreted to breast milk in humans.
Famciclovir does not have a pronounced effect on semen analysis, morphology or motility of sperm of man.
In experimental studies have revealed no embryotoxic and teratogenic effects of famciclovir and penciclovir.
Studies in rats treated with famciclovir orally showed that penciclovir is excreted in breast milk.
Reduced fertility was observed in experimental models in male rats treated with famciclovir 500 mg / kg of body weight, in rats female marked reduction of fertility has been noted.
Category of the fetus by FDA - B.
Use Famciclovir with caution in patients with impaired renal function.
In the presence of clinical manifestations of genital herpes even when the onset of antiviral treatment, patients should avoid sexual contact.
Famciclovir drug interactions
Probenecid and other drugs that affect renal function may change the level of penciclovir in plasma.